Paulo Vaz-Pires

Quality index method (QIM): development of a sensorial scheme for common octopus (Octopus vulgaris)

Abstract Sensory methods are the most accurate and widely used methods to evaluate fish freshness. This paper describes the development of a sensorial scheme for common octopus (Octopus vulgaris) based on the recent quality index method. The parameters for the basis of this new scheme are appearance, odour, mucus of skin, texture of flesh, cornea and pupil brightness, colour, odour and mucus in the mouth region, as well as the material found in the suckers. Octopus shelf-life is much shorter than that of fish species; as measured by sensorial attributes it is considered to be 8 days in ice.

Sensory, microbiological, physical and nutritional properties of iced whole common octopus (Octopus vulgaris)

The objective of this study was to collect general data about octopus as seafood and to clarify the validity of the methods for quality evaluation designed normally for other species. Sensory, microbiological and physical analyses were used to characterize whole raw common octopus (Octopus vulgaris) during storage in ice. Nutritional properties of the edible part were also determined. An adaptation of the EC scheme for cuttlefish and a recently developed Quality Index Method (QIM) table were used for sensory analysis. Shelf-life of whole octopus was estimated as 8 days, according to QIM, which is shorter than for most species. Microbiological results suggest that octopus can be better understood as food with knowledge of microbial counts, but the numbers found in octopus surfaces until rejection are lower than in fish, which suggests predominance of enzymatic (autolytic) degradation. Hydrogen sulphide producing bacteria constituted a significant proportion of the total aerobic flora. Physical analysis performed using the RT-Freshmeter showed this instrument can be applied to octopus and the results are useful as quality complementary information.

Conjugated linoleic acid in diets for large-size rainbow trout ( Oncorhynchus mykiss ): effects on growth, chemical composition and sensory attributes

The effects of graded levels (0 %, 0.5 %, 0.75 and 1 %) of dietary conjugated linoleic acid (CLA) were assessed on 97 g rainbow trout. Fish were fed to satiation twice a day for 12 weeks. At the end of the experiment, all groups of fish weighed more than 250 g and no significant differences were detected in growth performance, feed conversion, nutrient or energy utilisation or body composition between treatments. A decrease in liver lipid content resulted from including CLA and was accompanied by a reduction in malic enzyme activity. The muscle saturated acid and PUFA content did not vary between dietary treatments, despite the increasing concentration of stearic acid and CLA. In the liver, however, both fractions increased significantly with dietary CLA. Moreover, the MUFA decreased significantly in both muscle and liver. CLA was incorporated into tissue lipids, with levels in flesh (2.1-4.2 %) being 2-fold higher than in liver (0.8-1.9 %). In muscle, the percentage of cis-9, trans-11 isomer ranged from 39.5 % to 41.8 % and that of trans-10, cis-12 isomer from 31.4 % to 33.4 % of total CLA. The incorporation of CLA isomers in the liver varied with dietary treatment, and the cis-9, trans-11 isomer seemed to be more efficiently incorporated than trans-10, cis-12. Sensory data indicated slight-to-moderate differences between the trout fed with and without CLA. The present results suggest that 250 g rainbow trout can incorporate CLA in both muscle and liver, contributing to the production of a functional food.

Effect of Season on the Chemical Composition and Nutritional Quality of the Edible Crab Cancer pagurus

Cancer pagurus is most appreciated in southern Europe for its muscle and brown meat content. In Portugal, consumption occurs mostly in summer and at Christmas. In this study the seasonal nutritional quality of edible tissues of female and male C. pagurus was determined. Tissue composition was affected by season and sex. All tissues had a well-balanced essential amino acid composition. Muscle and gonads of females had n-3/n-6 ratios in the range of the usual recommended values, and all tissues had PUFA/SFA above the recommended level. Autumn was the season with the highest brown meat yield, total essential amino acids (muscle), taurine (all tissues), EPA (male gonads), and n-3/n-6 ratio (gonads). However, it was also the season with the highest fat content and cholesterol concentration in ovaries. Therefore, people with restricted diets should moderate the consumption of ovaries in autumn. The remaining tissues pose no risks with respect to their proximate chemical composition.

Effects of antimicrobial treatment on selection of resistant Escherichia coli in broiler fecal flora.

Under field conditions, three commercial antimicrobials were sequentially prescribed to 16,000 broiler chickens during their rearing period, via drinking water using subtherapeutic levels for 3 days. A control group of 16,000 broilers was placed in the same controlled environment poultry house. Feed diet and fecal samples from both groups were collected periodically. One sample of the drinking water along with samples from the broiler house environment was also collected 1 day before bird placement. Samples were plated onto Tergitol BCIG Agar media; a maximum of 26 Escherichia coli were isolated per sample, and their susceptibility was tested to 12 antimicrobials by disk diffusion agar method. We have observed that day-old chicks were rapidly colonized by new antibiotic-resistant patterns shortly after treatment with lincomycin associated with spectinomycin. After medication with the second (sulfadiazine with trimethoprim) and third (tylosin) antimicrobials, a more radical displacement was observed, and, concurrently, antimicrobial resistance phenotypes have become more complex. In contrast, more than 70% of the strains isolated in control group during the experiment displayed exactly the same resistance pattern found in the day-old chicks. This study provides clear evidence that a sequential medication of a broiler flock, with different antimicrobial classes during short periods of time for prophylactic objectives, was accompanied by a dramatic increase in both antimicrobial resistance rates and phenotype diversity of E. coli strains.

Antibiotic Resistance of Enterococcus spp. Isolated from Wastewater and Sludge of Poultry Slaughterhouses

Antibiotimicrobial resistance was investigated in 537 Enterococcus spp. isolates recovered from 22 samples of crude inflow, treated effluent and sludge collected in wastewater treatment plants of eight poultry slaughterhouses of Portugal. No significant differences (P > 0.05) were found in the resistance to each antimicrobial agent with regards to the origin of the sample (inflow, sludge and effluent). Many of the isolates displayed resistance to tetracycline (85.7%), erythromycin (45.7%), nitrofurantoin (34.0%) and rifampicin (17.8%). Resistance was also observed, but to a lesser extent, to ciprofloxacin (10.2%), ampicillin (8.0%), chloramphenicol (4.6%), vancomycin (0.9%) and gentamicin (0.4%). Resistance to three or more antimicrobial classes was present in 37.1% of the isolates. Wastewater treatment resulted in viable enterococci decrease between less than 1 log and 4 log; nevertheless, more than 4.4 × 105 colony forming units (CFU)/100 mL were present in the outflow of the plants and thus resistant enterococci are not prevented from reaching the general environment.

Nutritional quality of the edible tissues of European lobster Homarus gammarus and American lobster Homarus americanus.

The clawed lobsters Homarus gammarus and Homarus americanus are high-priced and appreciated food items in southern Europe. From a nutritional point of view there is still limited information on the chemical composition of edible tissues (muscle, hepatopancreas, and gonads) of both species. Therefore, the aims of the present work were to study the proximate chemical composition, energy, fatty acid and amino acid profiles, and cholesterol content in each edible tissue of both species and to evaluate their nutritional quality. Differences were observed between tissues, sexes, and species. Muscle and gonads were rich in protein, whereas hepatopancreas had high fat, cholesterol, and energy contents. All edible tissues were valuable sources of essential amino acids. Contrary to the common belief that shellfish consumption should be reduced in a low-fat and -cholesterol diet, all edible tissues of clawed lobsters have a nutritious value perfectly compatible with nutritious and healthy diets.

Influence of Season and Sex on the Contents of Minerals and Trace Elements in Brown Crab (Cancer pagurus, Linnaeus, 1758)

Cancer pagurus is much appreciated in Southern Europe, where the muscle, hepatopancreas, and gonads are consumed regularly with peaks in summer and December. The elemental contents of C. pagurus edible tissues were analyzed in this study during the four seasons. Results indicate that the content varied with tissue, season, and sex. The hepatopancreas had more S, Cl, Ca, Br, Sr, Fe, Cu, Cd, and Pb, the gonads had a higher concentration of Na, and the muscle was richer in Zn. Autumn and winter corresponded to a high Mg, S, Cl, K, Ca, Fe, and Zn content in both the muscle and hepatopancreas. Female gonads had more Fe, Zn, As, and Se than males but less Ca, Cl, Br, and Sr. Regarding toxic elements for human consumption, the levels of As, Hg, and Pb found in all edible tissues pose minimal risks to consumers. However, Cd concentration in the hepatopancreas was always above the action limit. Therefore, we recommend moderate hepatopancreas consumption.

High prevalence of multidrug-resistant Escherichia coli and Enterococcus spp. in river water, upstream and downstream of a wastewater treatment plant

In this study, microbial quality and antimicrobial resistance of faecal bacteria from a Portuguese river were assessed. River water samples collected upstream and downstream of a wastewater treatment plant, throughout a 3-month period, were used for the enumeration of Escherichia coli and Enterococcus spp. The highest numbers found for E. coli and enterococci were 1.1 × 10⁴ and 1.2 × 10⁴ colony forming units (CFU)/100 ml, respectively. In total, 144 isolates of E. coli and 144 of enterococci were recovered and tested for antimicrobial susceptibility; 104 E. coli and 78 Enterococcus spp. showed resistance to one or more antimicrobial drugs. Overall, 70 and 32 different resistance patterns were found for E. coli and enterococci, respectively. One E. coli showed resistance to imipenem and 29 isolates were extended spectrum β-lactamase-producers. Multidrug-resistant E. coli belonged mostly to groups A, B1 and group D. Enterococcus spp. were mostly resistant to rifampicin, tetracycline, azithromycin and erythromycin; six isolates showed resistance to vancomycin, presenting the VanA phenotype. The high levels of E. coli and enterococci and the remarkable variety of antimicrobial resistance profiles, reinforces the theory that these river waters can be a pool of antimicrobial resistance determinants, which can be easily spread among different bacteria and reach other environments and hosts.

Effect of MTGase, Dietary Fiber and UV Irradiation Upon Heat-Induced Gilthead Seabream (Sparus aurata) gels

The effects of microbial transglutaminase (MTGase, 0.5%, w/w), dietary fiber (konjac flour, Kjc, 1. 0%, w/w) and ultraviolet irradiation, UV (254 nm, 3300 µW/cm2 and 40 min), on heat-induced gels from gilthead seabream mince (Sparus aurata) were studied. MTGase addition improved texture, force at rupture increased from 44.3±18.1 to 131.9 ± 56.7 N, and increased pH and water-holding capacity. Moreover, MTGase reduced the elastic modulus E1 and darkened the gels; protein solubility declined, meaning greater protein aggregation, according to electropherograms. Evidence was found that disulfide bonding has a role in textural improvement by MTGase. Kjc increased the hardness from 15.1±3.1 to 20.6 ± 4.7 N, the elastic modulus and WHC. Kjc itself and not its effect upon proteins may explain the hardening effect. However, gels containing Kjc were less deformable and Kjc reduced the extractable protein in the various selective bond media. UV did not present advantages as a gelation-promoting technology. MTGase and Kjc were texturally advantageous, although without synergies for gel strength: it fell from 56.9±7.1 to 24.6±5.9 N mm as a result of adding Kjc to gels containing MTGase. Nevertheless, the hardening effect of Kjc and MTGase combined surpassed the sum of the individual effects, thereby indicating the existence of a mutual reinforcement of the hardness through MTGase and konjac. Additionally, this study showed that gilthead seabream may be used to produce good quality (concerning texture, color and WHC) heat-induced gels.